Alpha-olefin oligomers and their use as synthetic lubricants ("synlubes") are well-known. Early reports of such synlubes are in Seger et al. U.S. Pat. No. 2,500,161 and Garwood U.S. Pat. No. 2,500,163. U.S. Pat. No. 2,766,312 describes the oligomerization of .alpha.-olefins in a Group IV metal oxide bed using a BF.sub.3 promoter catalyst. Promoters include water, alcohol and ether.
U.S. Pat. No. 3,149,178 describes the preparation of a synlube by oligomerizing a C.sub.6-12 .alpha.-olefin thermally or using a Friedel Crafts or peroxide catalyst followed by distillation to remove dimer. The distillation residue is hydrogenated for use as a synlube. U.S. Pat. No. 3,382,291 discloses a BF.sub.3 -promoter (e.g. alcohol) process for making o-olefin oligomers in which the BF.sub.3 is used to saturate the o-olefin feed and a second stream of BF.sub.3 -promoter is fed to the reaction.
Synlubes used as automotive crankcase lubricants have viscosities in the range of 4-8 cs at 100.degree. C. These are usually mixture of trimers, tetramers and pentamers of C.sub.8-12 .alpha.-olefins, especially 1-decene.
Recently extra high viscosity ("XHVI") mineral oil lubricants have been made available by new refining technology. Such XHVI oils have viscosity indices in the range of 145. These can be used as blending agents with lower viscosity mineral oil to obtain a blended oil suitable for use in an engine crankcase which approaches the performance of poly-alpha-olefin ("PAO") synlubes. It would be useful to be able to make an oil equivalent to XHVI mineral oil from olefin monomers.